The present invention relates to a device for deshirring or unfolding, smoothing and braking or restricting the movement of a shirred tubular casing during the filling of the casing with a fluid material such as a sausage mixture. The invention further relates to an apparatus containing such a device and to an article of manufacture containing such a device.
It is known to use shirred tubular casings of synthetic, semi-synthetic or natural materials for packing food products, for example meat products in the form of sausages. These shirred casings, which are known in the trade as "sticks" or "hollow rods", are produced by gathering and longitudinally compressing long casings to approximately one to three percent of their original length. In order to fill the shirred casing with a sausage mixture or other food product, generally, one end of the shirred casing is first closed, and then the shirred casing is normally fit onto the filling tube or stuffing horn of a sausage machine. A sausage mixture is then forced under pressure through the stuffing horn into the casing which is thereby continuously unfolded or deshirred. After a predetermined length of the casing has been filled, the filled casing is subdivided into cylindrical sausages which are then tied off and closed.
For various reasons, the diameter of the sausages which are produced should remain constant throughout their entire length. Optimum filling of the tubular casing can be assured only by a uniform diameter, the size of which is dependent upon the particular casing. If the casing is overstuffed, it may burst, whereas if the casing is insufficiently filled, it will have a wrinkled surface.
Various devices for stuffing shirred tubular casings with sausage mixtures have been proposed which comprise special arrangements for achieving the most uniform diameter possible for the filled casings.
Thus, it is conventional to dispose adjacent the outlet of the stuffing horn, a calibrating means, the periphery of which presses against the inside wall of the casing to be filled and expands the casing. The contact pressure between the calibrating means and the inside wall of the casing gives rise to frictional forces which brake or retard the motion of the casing (U.S. Pat. No. 2,871,508).
It is also known to package the shirred tubular casing together with a calibrating disk and to connect this assembly to the stuffing horn of a sausage machine prior to the filling operation. The calibrating disk is enclosed or surrounded by an unshirred portion of the casing, whereby the outer circumference of the calibrating disk should be larger than the internal circumference of the deshirred casing. During the filling operation, the casing is drawn over the calibrating disk and is thereby stretched and expanded (U.S. Pat. No. 4,077,090). The calibrating disk must be made of a rigid, inelastic material so that its diameter will not be altered by the contact pressure of the casing against the periphery of the calibrating disk. Braking of the casing as it is withdrawn from the shirred portion during the filling operation is effected by means of an auxiliary device having the form of a ring with an annular attachment disposed following the calibrating disk whereby the braking effect is controlled by the frictional forces produced between the tubular casing and the attachment.
These inelastic calibrating disks have the disadvantage that the variations in casing circumference which cannot be avoided during the manufacturing process, will prevent optimum filling of the casing from being achieved. If the diameter of the casing is too small, there is a danger that the casing may be damaged or torn by the calibrating disk. At the very least, an especially strong frictional force will arise between the casing and the calibrating disk so that the casing will be overfilled with sausage mixture and have a tendency to be unable to withstand the high pressures which arise during boiling of the sausage and to burst.
U.S. Pat. No. 4,202,075 discloses a calibrating means which is made of a flexible material and has a variable diameter. This device is also intended to stretch and expand the tubular casing prior to the casing being filled with a sausage mixture, while the device provides a controllable degree of expansion. Even with this device, however, strong frictional forces can occur between the tubular casing and the calibrating means. With this device, the braking of the tubular casing is effected by means of a braking element which is disposed after the calibrating device and which presses the tubular casing against the stuffing horn.